Primate T-cell leukemia viruses (PTLVs) are genetically diverse deltaretroviruses comprised of simian and human T-cell leukemia viruses (STLVs and HTLVs, respectively). Like human immunodeficiency virus (HIV), HTLV is a zoonotic simian retrovirus originating from historical and contemporary contact with STLV-infected nonhuman primates (NHPs). The genetic diversity of HTLV is directly related to the genetic diversity of the STLVs from which the primary zoonotic infection originated, as evidenced by the clustering of geographically proximal HTLVs and STLVs within the same phylogenetic lineages. Four PTLV groups have been identified: PTLV-1, PTLV-2, PTLV-3 and PTLV-4. PTLV-1, PTLV-2 and PTLV-3 include human (HTLV-1, HTLV-2, and HTLV-3) and simian (STLV-1, STLV-2, and STLV-3) viruses. PTLV-4 comprises HTLV-4, which was identified from one individual in Cameroon with known exposure to primates. A simian counterpart of this virus has not yet been identified (Wolfe et al. Proc. Natl. Acad. Sci. U.S.A. 102:7994-7999, 2005).
HTLV-1 and HTLV-2 are known to be transmitted through sexual contact (Murphy et al. Ann. Intern. Med. 111:555-560, 1989); mother-to-child transmission through breastfeeding (Hino et al. Jpn. J. Cancer. Res. 1985, 76:474-480, 1985; Vitek et al. J. Infect. Dis. 171:1022-1026, 1995); transfusion of blood and/or blood products (Maims et al. Int. J. Cancer 51:886-891, 1992; Okochi and Sato Princess Takamatsu Symp. 15:129-135, 1984; Okochi et al. Vox. Sang. 46:245-253, 1984); and injection drug use (Van Brussel et al. Rev. Med. Virol. 9:155-170, 1999). The mechanisms of transmission of PTLVs and other retroviruses between primates and humans are largely unknown, but it is believed that humans can become infected with simian retroviruses through direct exposure to primates via bites or scratches or contact with body fluids from butchering and handling infected bushmeat (Wolfe et al. Proc. Natl. Acad. Sci. U.S.A. 102:7994-7999, 2005; Wolfe et al. Lancet 363:932-937, 2004).
Many of the PTLV strains and subtypes have been described from human and primate samples derived from central Africa. In addition to the recent discovery of HTLV-3 (Wolfe et al. Proc. Natl. Acad. Sci. U.S.A. 102:7994-7999, 2005; Calattini et al. Retrovirology 2:30, 2005) and HTLV-4 (Wolfe et al. Proc. Natl. Acad. Sci. U.S.A. 102:7994-7999, 2005) from primate hunters in southern Cameroon, HTLV-1 subtypes B, D and E (Mahieux et al. J. Virol. 71:1317-1333, 1997; Salemi et al. Virology 246:277-287, 1998) and HTLV-2 subtypes B and D (Vandamme et al. J. Virol. 72:4327-4340, 1998) have been isolated from inhabitants of this region. Similarly, STLV-1, found in the HTLV-1 subtype B clade, has been identified in Cameroonian gorillas (Gorilla gorilla) and chimpanzees (Pan troglodytes vellerosus) (Nerrienet et al. J. Gen. Virol. 85:25-29, 2004) and STLV-3 has been found in wild-caught red-capped mangabeys (Cercocebus torquatus) from Nigeria and Cameroon (Meertens et al. J. Gen. Virol. 84:2723-2727, 2003). Furthermore, evidence for dual infections of STLV-1 and STLV-3 in agile mangabeys (Cercocebus agilis) in Cameroon has also been reported (Courgnaud et al. J. Virol. 78:4700-4709, 2004). These studies suggest that humans are exposed to a significant number of PTLVs in west and central Africa. Therefore, the need exists for methods of detecting viral infections, for example to monitor the transmission of such viruses into the human population. In addition, the need exists for vaccines for such viruses, for example by producing an immune response to peptides isolated from such viruses. However, it is not possible to vaccinate populations against organisms not known to exist, nor can such unknown organisms be detected and followed in a population at risk of infection.